//
//  ObjectPool.hpp
//  ConcurrentMemoryPool
//
//  Created by 张木林 on 4/2/25.
//


#include "Common.hpp"

#ifdef _WIN32
#include <windows.h>

#else

#endif



template<class T>
class ObjectPool
{
public:
    T* New()
    {
        T* obj = nullptr;

        // 优先把还回来内存块对象，再次重复利用
        if (_freeList)
        {
            void* next = *((void**)_freeList);
            obj = (T*)_freeList;
            _freeList = next;
        }
        else
        {
            // 剩余内存不够一个对象大小时，则重新开大块空间
            if (_remainBytes < sizeof(T))
            {
                _remainBytes = 128 * 1024;
                //_memory = (char*)malloc(_remainBytes);
                _memory = (char*)SystemAlloc(_remainBytes >> 13);
                if (_memory == nullptr)
                {
                    throw std::bad_alloc();
                }
            }

            obj = (T*)_memory;
            size_t objSize = sizeof(T) < sizeof(void*) ? sizeof(void*) : sizeof(T);
            _memory += objSize;
            _remainBytes -= objSize;
        }

        // 定位new，显示调用T的构造函数初始化
        new(obj)T;

        return obj;
    }

    void Delete(T* obj)
    {
        // 显示调用析构函数清理对象
        obj->~T();

        // 头插
        *(void**)obj = _freeList;
        _freeList = obj;
    }

private:
    char* _memory = nullptr; // 指向大块内存的指针
    size_t _remainBytes = 0; // 大块内存在切分过程中剩余字节数

    void* _freeList = nullptr; // 还回来过程中链接的自由链表的头指针
};

struct TreeNode
{
    int _val;
    TreeNode* _left;
    TreeNode* _right;

    TreeNode()
        :_val(0)
        , _left(nullptr)
        , _right(nullptr)
    {}
};

void TestObjectPool()
{
    // 申请释放的轮次
    const size_t Rounds = 5;

    // 每轮申请释放多少次
    const size_t N = 100000;

    std::vector<TreeNode*> v1;
    v1.reserve(N);

    size_t begin1 = clock();
    for (size_t j = 0; j < Rounds; ++j)
    {
        for (int i = 0; i < N; ++i)
        {
            v1.push_back(new TreeNode);
        }
        for (int i = 0; i < N; ++i)
        {
            delete v1[i];
        }
        v1.clear();
    }

    size_t end1 = clock();

    std::vector<TreeNode*> v2;
    v2.reserve(N);

    ObjectPool<TreeNode> TNPool;
    size_t begin2 = clock();
    for (size_t j = 0; j < Rounds; ++j)
    {
        for (int i = 0; i < N; ++i)
        {
            v2.push_back(TNPool.New());
        }
        for (int i = 0; i < N; ++i)
        {
            TNPool.Delete(v2[i]);
        }
        v2.clear();
    }
    size_t end2 = clock();

    cout << "new cost time:" << end1 - begin1 << endl;
    cout << "object pool cost time:" << end2 - begin2 << endl;
}
